The present invention relates to a retainer for a needle roller bearing.
FIG. 9 shows a conventional outer-diameter guide type retainer for a needle roller bearing. It comprises opposite annular portions 1 and a plurality of integral crossbar portions 2 extending between the annular portions 1 and arranged circumferentially at equal intervals. Needle rollers 3 are received in pockets 4 defined between the adjacent crossbars 2. Both sides of the crossbars 2 serve as guide surfaces 5.
The outer surfaces of the annular portions 1 and the crossbar portions 2 are of the same height (or radius) and form outer-diameter guide surfaces 6 for the retainer itself.
Each crossbar has two pairs of outer-diameter claws 7 in its outer peripheral surface, each pair being longitudinally spaced from each other and protruding from each guide surface 5 into the pocket 4. Four pairs of inner-diameter claws 8 similar to the claws 7 are provided in the inner periphery of each crossbar 2 near both ends.
The needle rollers 3 are snap-fitted in the pockets 4 by resiliently deforming the crossbars 2 and are retained in the pockets by the outer-diameter claws 7 and the inner-diameter claws 8.
The claws 7 and 8 are formed by partially caulking, molding or ironing the crossbars 2.
A needle roller bearing having such a retainer is disposed between two relatively rotating members so that its outer-diameter guide surfaces 6 are guided by the outer one of the two relatively rotating members.
In the case of an inner-diameter guide type retainer, the inner peripheral surfaces of the annular portions 1 and the crossbar portions 2 are used as inner-diameter guide surfaces which are guided by the inner rotary member.
The outer-diameter claws and the inner-diameter claws protrude from both sides of each crossbar near its outer-diameter and inner-diameter surfaces. In the case of an outer-diameter guide type retainer, the outer-diameter claws tend to break a film of lubricating oil formed between the retainer and the mating member, or in the case of an inner-diameter guide type retainer, the inner-diameter claws tend to break an oil film. When rollers are brought into contact with mating members at portions where oil films are broken by the inner or outer claws, the rollers tend to suffer peeling at the contact portions.
An object of the present invention is to provide a retainer for a needle roller bearing having inner and outer roller retaining claws arranged so as not to break an oil film formed on the retainer, irrespective of whether the retainer is the outer-diameter guide type or the inner-diameter one.